Electric circuit breaker



L.. s. HoBsoN ELECTRIC CIRCUIT BREAKER Filed May 17, -1955 May l, 1934.

Patented May 1, 1934 Leland S. Hobson,

General Electric Company,

New York ELECTRIC CIRCUIT BREAKER Folcroft, Pa., assignor to acorporation of Application May 17, 1933, Serial No. 671,496

Claims.

My invention relates to electric circuit breakers, more particularly tothe means for mechanically and electrically connecting the stationarycontact adapter to the lead-in conductor of the circuit breaker.Heretofore the use in a circuit breaker of clamp unions or jointsbetween the lead-in conductor stud and stationary Contact adapter hasfro quently been the source of excessive heating of the circuit breakerdue to poor electrical connection between the adapter and stud. Thesemembers, posed of copper, are sometimes separated lead-in conductorwhich are generally com* at their contact surfaces by an oxide filmwhich, together with the low pressure per unit contact area produced bythe clamping means, results in paratively high resistance union members.ticularly in heavy duty dling large currents, in

circuit breakers f between said Such a high resistance union, parorhanturn results in excessive heating at the rated capacity of thecircuit breaker. since the specifications for heavy duty This is anextremely undesirable situation circuit breakers generally limit thecircuit breaker to a definite temperature rise at its rated cap Myinvention has for its provision of improved means effecting acity.

principal object the the mechanical and electrical connection betweenthe lead-in conductor stud and stationary adapter of a circuit breaker.

Contact My invention will be more fully set forth in the followingdescription referring to the panying drawing, and the features of whichcharacterize my invention will be accomnovelty pointed out withparticularity in the claims annexed to and forming a part of thisspecification.

Referring to the drawing, Fig. 1 is a fr tary view, partly in section,of a circuit agmenbreaker embodying my invention.

In Fig. 1 there is shown, by way of example, a

' contact structure for an oil circuit breaker comprising a verticallymovable bridging member l and stationary contacts 2 and 3 adapte dto beengaged and interconnected by the bridging member in its elevated Theaforesaid Contact structure mersed in a of a well known type whichclosed circuit position.

is imsuitable insulating liquid, as oil, is wherein each stationarycontact comprises a plurality of pairs of resiliently mounted fingercontacts as indicat and 3, respectively, which are engag ed at 2 ed and(Cl. ZOO- 150) spread apart by the wedge-shaped (in transverse crosssection) bridging member 1. They stationary contact structure likewisecomprises a contact adapter 4 cn which are suitably mounted inconducting relation, as at 5, the aforesaid contact fingers. The adapteris formed as a bar or biock of conducting material, as copper, and ismechanically supported by and electrically connected to the circuitbreaker lead-in conductor 6 in a manner hereinafter described.

Each lead-in conductor 6 comprises a tubular conductor stud of copper,or the like, provided with an insulating sleeve l extending to the unionwith the adapter 4 which is provided with a mem- 8 forming a partthereof. The member 8 is arranged to extend within and be secured to thelower end of the tubular conductor stud 6, the conductor stud and member8 having screwthreaded engaging surfaces for the purpose as illustrated.

For the purpose of effecting a tight mechanical union and a lowresistance electrical connection between the adapter member 8 and theconductor stud 6, a slot 9 and a central aperture l0 are formedcentrally and axially of the member 8. 80 rihe lower portion of thecentral aperture 10 is formed as a screw tap and the upper portion ofthe opening is flared to form a conical wedging surface 11 which coactswith a corresponding conical wedging surface 12 of an adjusting screw13. The slot 9 provides suicient resilience for the member 8 to beexpanded by the adjusting screw into high pressure contact engagementwith the conductor stud 6.

The adjusting screw 13 is in its normal position as illustrated in Fig.l. The connection and disconnection of the contact adapter with respectto the conductor stud is made apparent by Fig. 2. In connecting theaforesaid members the adjusting nut 13 is rst started into the adapter4. after which the adapter with the adjusting nut is inserted andscrewed into the lower end of the conductor stud. When the adapter 4 hasbeen screwed to the correct contact position, the adjusting nut 13 issecurely tightened by a socket wrench extending through the conductorstud.

It will be apparent that the expanding force on the member 8 due to theengaging conical surfaces 11 and 12 will be high, depending of course onthe angie of the wedging surfaces, so that the adapter is forced intohigh unit pressure engagement with the conductor stud. Furthermore, thecoacting screw-threaded engaging surfaces tend to form in effect aplurality of high pressure line contact areas with the result that a.very good CII low resistance electrical connection is provided betweenthe conductor stud and the stationary contact adapter.

In view of the comparatively low resistance at the conductorstud andadapter union, there will be no tendency for the screw threads to heatexcessively, and disconnection of the adapter for the purpose of repairor replacement is greatly facilitated.

In Fig. 3 a modied form of the above described arrangement is shownwherein the adjusting screw 20 coacts with a rustro-conical nut 21within the adapter member 8, the screw 20 in the present case enteringthe member 8 from beneath through the bore 22. The nut 21 may obviouslybe forced into wedging engagement with the member 8 in the manner abovedescribed so as to expand the same into high pressure engagement withthe conductor stud 6. The screw 20 is provided with the usual screw head20 so that assembly and final tightening of the adapter unit issimplied.

As in the previous case, the screw 20 is rst started from beneath intothe adapter block, the nut 21 being seated within the recess defined bythe wedging surface 11 so as to receive the threaded end of the screw20. The adapter member 8 is then screwed into the conductor stud untilthe contact-adapter is properly located. The assembly is completed bysuitably tightening the screw 20 as indicated at 20. The abovearrangement has obvious advantages, particularly where the lead-inconductor stud is of appreciable length.

In both constructions shown, it will bc noted that proper adjustment ofthe adapter can be quite easily secured. These necessary adjustmentsinclude, rst, proper height with respect to the movable bridging member.This is secured by turning the adapter in or out of the threads,depending on whether the adapter is to be raised or lowered. Thisadjustment is necessary in order to obtainl the proper contact pressureson the electrically connecting said adapted to said conment is theproper alinement of the adapter, which is readily secured by slightrotation of the adapter. This makes possible proper contact pressures onthe entire group of stationary contact fingers. After the properadjustments are completed, the adapter is effectively locked to theconductor stud in proper position by expanding the adapter 8 in themanner above described.

The mechanical connection between the conductor stud and adapterinvolves a number of advantages in circuit breaker constructionincluding simplicity, compactness in design, mechanical strength andruggedness, and low cost because of the use ci less copper and the easeof assembly. Furthermore, the absence of clamping rings cr couplingsbetween the adapter and conductor stud enables the conductor stud to beinsulated throughout its entire length as illustrated in Fig. l. In viewof the fact that the coupling means in the present instance is located,at least in part, within the conductor stud which extends through thecircuit breaker cover, the overall length of the contact adapter andconductor stud may be comparatively limited. In other words, the contactadapter could be located nearer the metallic cover structure of thecircuit breaker tank than the type of adapter wherein COmlJal'ativelywide external clamping ring forms the union between the conductor studand adapter.

It should be understood that my invention is not limited to specificdetails of construction and arrangement thereof herein illustrated, andthat changes and modifications may occur to one skilled in the artwithout departing from the spirit of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In an electric circuit breaker including a tubular lead-in conductorstud and a stationary contact adapter, means for mechanically andelectrically connecting said adapter to said conductor stud comprising amember forming part of said adapter extending into one end of said stud,and an adjustable Wedging member positioned centrally of said adaptermember for expanding the same into high pressure engagement with saidconductor stud.

2. In an electric circuit breaker including a tubular lead-in conductorstud and a stationary contact adapter, means for mechanically andelectrically connecting said adapter to said conductor stud comprising amember forming part of said adapter extending into one end of said stud,said member having a slot and an tending axially and centrally thereof,and a wedging member positioned in said aperture for expanding saidadapter member into highipressure engagement with said conductor stud.

3. In an electric circuit breaker including a tubular lead--in conductorstud and a stationary contact adapter, means forming an adjustablemechanical and electrical union between said adapter and stud comprisinga member forming part of said adapter ductor stud and havingscrew-threaded engagement therewith, said member having a centrallydisposed aperture, and a wedging member located within said aperture andadapted to engage said adapter member so as to extend said member intoj' high pressure contact engagement with and to lock the same to saidconductor stud.

4. In an electric circuit breaker including a tubular lead-in conductorstud and a stationary contact adapter, and electrical union between saidstud and adapter comprising a member forming part of said adapterextending within said stud, said member and stud being in screw-threadedengagement,

said member having a slot extending axially i thereof and a centrallydisposed aperture terminatfng in a screw tap, and an adjusting wedgingscrew disposed within said aperture and coacting with said screw tap,said screw having a conical wedging surface coacting with acorresponding siuface in said member for expanding said member into highpressure Contact engagement with said stud.

5. In an electric circuit breaker including a tubular lead-in conductorstud and a stationary contact adapter, means forming an adjustablemechanical and electrical union between said stud and adapter comprisinga member forming part of said adapter extending within one end of saidstud, said adapter having a bore extending centrally of said member,said bore terminating in a conical-shaped recess, a nut having a wedgingsurface corresponding to said conical recess and seated within saidrecess, and a screw extending through said bore and coacting with saidnut for expanding said adapter member into high pressure Contactengagement with said stud.

LELAND S. HOBSON.

extending into said conj' means forming a mechanical I aperture ex- .":1

CERTIFICATE 0F CORRECTION.

Patent No. 1,957,213. May l, 1934.

LELAND S. HOBSON.

It is hereby certified that errer appears in the printed specificationof the above numbered patent requiring correction as follows: Page 2,lines 44 and 45, strike out the words "electrically connecting saidadapted to said conment" and insert instead bridging member. The secondessential adjustment; and that the said Letters` Patent should be readwith this correction therein that the same may conform to the record ofthe case in the Patent Office.

Signed and sealed this 19th day of June, A. D. 1934.

Bryan M. Battey (Seal) Acting Commissioner of Patents.

CERTiFlCA'E 0F CORRECTION.

Yatent No. 1,957,213. May 1, 1934.

LELAND S. HOBSON.

it is hereby certified that error appears in the printed specificationof the above numbered patent requiing corfeetion as foliows: Page 2,lines 44 and 45, strike out the words "eieetricaiiy connecting saidadapted to said conment" and insert instead bridging member. The secondessential adjustment; and that the said Letters Patent should be reatiwith this correction therein that the same may conform to the record ofthe case in the Patent Office.

Signed and sealed this 19th day of June, A. D. 1934.

Bryan M. Battey (Seal) Acting Commissioner o Patents.

